Powder coating compositions for use in industrial and automotive coating applications, such as coatings for metal substrates, are extremely desirable. Such coating compositions can eliminate the organic solvents used in liquid coating compositions. When a powder coating composition is thermally cured, little, if any, volatile material is given off to the surrounding environment. This is a significant advantage over liquid coatings in which an organic solvent is volatilized into the surrounding atmosphere when the coating is cured by heating.
Additionally, powder coating compositions, which can be prepared by mixing all of the components together in a single medium, are desirable from a formulation perspective. However, the preparation of powder coating compositions based on carbodiimide compounds and compounds containing carboxylic acid functional groups have been conventionally difficult because the crosslinking reaction tends to take place too rapidly, resulting in coating systems having short pot-life and that are not satisfactorily flowing.
As a result, it would be desirable to provide improved methods for preparing powder coating compositions based on carbodiimide compounds and compounds containing carboxylic acid functional groups.